Add ternary logic type maybe_bool.

3 files changed, 37 insertions, 0 deletions

diff --git a/crawl-ref/source/enum.h b/crawl-ref/source/enum.h
index c970478866..d14fd76c9a 100644
--- a/crawl-ref/source/enum.h
+++ b/crawl-ref/source/enum.h
@@ -3167,6 +3167,13 @@ enum montravel_target_type
     MTRAV_KNOWN_UNREACHABLE // As above, and the player knows this.
 };
 
+enum maybe_bool
+{
+    B_FALSE,
+    B_MAYBE,
+    B_TRUE
+};
+
 #ifdef USE_TILE
 enum screen_mode
 {
diff --git a/crawl-ref/source/stuff.cc b/crawl-ref/source/stuff.cc
index f7f93c67a7..f3d24c6f25 100644
--- a/crawl-ref/source/stuff.cc
+++ b/crawl-ref/source/stuff.cc
@@ -936,3 +936,29 @@ int random_rod_subtype()
 {
     return STAFF_FIRST_ROD + random2(NUM_STAVES - STAFF_FIRST_ROD);
 }
+
+maybe_bool frombool(bool b)
+{
+    return (b ? B_TRUE : B_FALSE);
+}
+
+bool tobool(maybe_bool mb)
+{
+    ASSERT (mb != B_MAYBE);
+    return (mb == B_TRUE);
+}
+
+bool tobool(maybe_bool mb, bool def)
+{
+    switch (mb)
+    {
+    case B_TRUE:
+        return (true);
+    case B_FALSE:
+        return (false);
+    case B_MAYBE:
+    default:
+        return (def);
+    }
+}
+
diff --git a/crawl-ref/source/stuff.h b/crawl-ref/source/stuff.h
index 11fea7beed..5bfcebdcd2 100644
--- a/crawl-ref/source/stuff.h
+++ b/crawl-ref/source/stuff.h
@@ -97,4 +97,8 @@ int integer_sqrt(int value);
 
 int random_rod_subtype();
 
+maybe_bool frombool(bool b);
+bool tobool(maybe_bool mb, bool def);
+bool tobool(maybe_bool mb);
+
 #endif